(subclass Pterygota, order Coleoptera)
Family of shiny, aquatic beetles with paddle-like swimming legs, found in slow-moving water. Formerly they were placed in Dytiscidae, but they are distinguishable by their more flattened ventral surface and more convex dorsal surface. Each larva has a long body, walking legs, and large, curved jaws, and taps air spaces of aquatic plants for oxygen. Adults and larvae prey on soft-bodied larvae and snails.
Subjects: Zoology and Animal Sciences.